Growth and characterizations of magnetic nanoparticles under hydrothermal conditions: Reaction time and temperature

• Iron oxide with different nano-sizes and properties was generated by a hydrothermal method.
• The initial nanoparticles were synthesized by coprecipitation.
• The sizes of particles from TEM images were 14±4 nm and 74±9 nm for 1 h and 120 h, respectively.
• Ms of the samples increased from 74.9 to 93.5 emu/g as a result of growth of particle size.
• Hs decreased from 8698 to 2773 Oe as a result of growth of particle size with reaction time.

Magnetic iron oxide nanoparticles with various sizes and magnetic properties were synthesized by using a hydrothermal method. The initial nanoparticles were obtained by co-precipitation of ferric and ferrous salts and then treated under a hydrothermal condition for 1–120 h at 160 °C. At reaction time of 12 h, further treatment on the particles was performed at 200 °C. The resultant nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffractometer (XRD) and vibrating sample magnetometer. The images obtained by TEM showed that the particles are around spherical in shape. The mean size of particles increased from 14±4 nm to 74±9 nm as the reaction time was increased from 1 h to 120 h. From the XRD patterns, high crystalline iron oxide nanoparticles were obtained with increasing reaction time and temperature. The saturation magnetizations obtained from magnetization curves were found to be rising from 74.9 to 93.5 emu/g that is consistent with the bulk value of the magnetite.